A polymer electrolyte fuel cell using a proton conductive solid polymer membrane operates at a low temperature in comparison to other types of fuel cells, for example, a solid oxide fuel cell or a molten carbonate fuel cell. For this reason, the polymer electrolyte fuel cell has been expected to be used as a power source for energy storage system or a driving power source for a vehicle such as a car, and practical uses thereof have been started.
In general, such a polymer electrolyte fuel cell uses expensive metal catalyst represented by platinum (Pt) or a Pt alloy, which leads to high cost of the fuel cell. Therefore, development of techniques capable of lowering the cost of the fuel cell by reducing a used amount of noble metal catalyst has been required.
For example, Patent Literature 1 discloses an electrode catalyst having catalyst metal particles supported on a conductive support, wherein an average particle diameter of the catalyst metal particles is larger than an average pore diameter of fine pores of the conductive supports. The Patent Literature 1 discloses that, according to the above-described configuration, the catalyst particles are not allowed to enter the fine pores of the supports, so as to increase a ratio of the catalyst metal particles used in a three phase boundary, and thus, to improve use efficiency of expensive noble metal.